Under certain atmospheric and flight conditions, ice may tend to form on the leading edge or lip of a jet engine nacelle. This ice buildup on the lip skin will, of course, cause damage to the engine fan blades if allowed to build up, break loose and be ingested. It is therefore desirable to de-ice the lip skin during flight. To this end, hot engine air is ducted into the annular space between the forwardmost bulkhead of the nacelle and the lip skin. The hot air enters at one location, travels circumferentially around the annular space and exits at another location.
To assure that de-icing air is always available, the valve that controls the de-icing air is designed to fail in an open mode. However, when the valve fails in an open mode, high velocity hot air continuously travels through the circumferential space behind the lip skin raising the air temperature sometimes to on the order of 600 to 800 degrees. To insulate the structure and components mounted in the nacelle rearwardly of the first bulkhead, insulation blankets are installed. However, prior art insulation blankets cannot satisfactorily withstand the high temperatures and high air velocities that are encountered in an open-valve, failure mode of operation.